When the operator of an information system changes the setting of the system or updates an application, a setting change error, a bug in the new version and the like may cause a trouble in the service. The snapshot of a virtual machine has been used in order to immediately restore the previous condition when such a situation arises.
The restoring using the snapshot of a virtual machine refers to a function with which the condition of the virtual machine is saved, enabling the restoring of the machine to the condition at a later time.
As a first technique, there is a technique with which, when the snapshots of a plurality of virtual computers communicating with each other area are created simultaneously, the technique is performed in a condition maintaining integrity without losing the data being transmitted (for example, Patent document 1). In the first technique, when saving the snapshots of guest OSs (Operating Systems) A, B, saving execution units A, B give instructions to virtual network drivers A, B on the management OS side to stop the storing of data in network transmission queues by the guest OSs A, B, wait until the network transmission queues A, B and network reception queues A, B become empty, and when these queues become empty, outputs snapshot instructions to VM monitors A, B, to make them save the snapshot of the condition of the virtual hardware of the guest OSs A, B.
As a second technique, there is a technique in which a host server hosting one or a plurality of virtual machines backs up the host volume and one or a plurality of virtual machines installed in it by an application integrity method (for example, Patent document 2). In the second technique, the requester of the host level gives an instruction to the writer of the host level to identify which virtual machine is appropriate for application integrity back up. Next, the requester of the host level gives an instruction to the writer of the host level to start virtual machine backup, through the requester of the guest level in each virtual machine configured appropriately. The virtual machine creates an application integrity backup in the virtual machine volume. Next, the requester of the host level starts the snapshot of the server volume on the host level. Therefore, the snapshot of the virtual machine level may be taken out of the snapshot of the host level of the server volume.
As the third technique, there is a technique with which the condition of the virtual computer may be restored to the point of time of the occurrence of a failure, without making the output to the outside of the system wait, regardless of the condition to maintain integrity with the outside (for example, Patent Document 3). In the third technique, a communication recording apparatus records the communication data input/output between the external system and the virtual computer in time series as the communication log. When the restoring of the virtual computer is needed due to an occurrence of a failure, a snapshot management mechanism restores the virtual computer to the point of the time of the capture of the snap shot (a first point of time), based on the latest snapshot of the virtual computer. A log reproduction mechanism inputs, in time series to the virtual computer, the input data from the first time to a second point time that is the time of the occurrence of the failure, to restore the virtual computer to the second point of time.
As a fourth technique, there is a technique with which, when virtual cooperating machines are temporarily stopped, the integrity between the cooperating virtual machines is maintained at the time of resumption (for example, Patent document 4). In the fourth technique, the management server manages physical machines and also manages a plurality of virtual machines deployed on the physical machines, and the execution of the control process is enabled by mutual cooperation between the plurality of virtual machines. The management server includes a dependency list creating unit, a target managing table creating unit, a target presenting unit. The dependency list creating unit creates a dependency list table that manages the dependency of the virtual machines. Upon detecting a selection instruction for the virtual machine being the target of a temporary stop, the target managing table creating unit creates a temporary stop order managing table to manage all the virtual machines that have a dependency with the virtual machine, based on the dependency list table. The target presenting unit presents all the virtual machines being the temporary stop target in descending order of dependency, based on the temporary stop order managing table.
As the fifth technique, when a failure occurs in a physical computer on which a virtual machine is running, the service is continued by a virtual machine re-generated or re-started on another physical computer (for example, Patent document 5). In the fifth technique, when a failure occurs in a server computer on which a virtual machine is running, the virtual machine monitor of the server computer re-generates the virtual machine as a virtual machine on the server computer, based on a snapshot obtained on a disk apparatus at the nearest point of time to the time of the occurrence of the failure. The condition reproducing unit of the communication recording unit makes the virtual machine reproduce the condition of the virtual machine in the period from the time in which the snapshot was obtained to the time of the occurrence of the failure, based on the communication history associated with the virtual machine. The re-starting unit re-starts the virtual machine on the server computer, in the case of a failure in reproducing the condition of the virtual machine, for example.
Patent document 1: Japanese Laid-open Patent Publication No. 2011-253350
Patent document 2: Japanese National Publication of International Patent No. 2009-533777
Patent document 3: Japanese Laid-open Patent Publication No. 2009-80705
Patent document 4: Japanese Laid-open Patent Publication No. 2009-245317
Patent document 5: Japanese Laid-open Patent Publication No. 2009-80692